Two-way radios are radio communication devices that transmit and receive radio signals which typically are modulated voice or audio signals. Two-way radios typically use half duplex operation where they can either transmit or receive, but not both at the same time. In an idle state a two-way radio monitors one or more selected radio channels, and a PTT switch. If the two-way radio detects a signal on the monitored channel or channels, it begins to receive the transmitted signal. By “receive” it is meant that the transmitted information is demodulated and processed for perception by the user, or other operation by the two-way radio that is beyond merely monitoring the channel or channels. Once the monitoring detects a signal in a monitored channel, the two-way radio changes from the idle state to a receive state. When audio signals are received over the channel, they are played over a speaker connected to, or integrated with the two-way radio. Generally the audio signals are played at a volume level sufficient to be heard by the two-way radio user at a distance from the two-way radio. Similarly, while in the idle state, if the user keys up the radio by pressing and holding a PTT button, the two-way radio will immediately transmit, or attempt to transmit. Typically, it is the user's voice being transmitted, and more sophisticated two-way radios will, upon the PTT button being keyed (held), check to make sure the channel is available.
Given the immediacy of communication over other forms of wireless communication, such as, for example, cellular telephony, two-way radio communication has maintained popularity, especially in situations where immediate communication can be essential, such as in public safety operations (e.g. police, fire, rescue). While two-way radios made for public safety organizations tend to be sophisticated, feature-rich devices, there is also a market for low cost two-way radios, with fewer features, referred to as “low tier” radios. Two-way hand held portable radios (as opposed to, for example, vehicle mounted radios) are typically designed to be operable with accessories, ranging from a simple earphone audio jack to more sophisticated accessories. One feature that is provided in more the more expensive and sophisticated two-way radios is voice activated transmit operation, where the user's voice, rather than the PTT switch, controls transmission. With voice controlled transmission, when the audio energy at the microphone exceeds a threshold, the radio begins transmitting. Simple accessory connectors do not offer the ability to provide sophisticated accessory operation, however, and the control lines used for accessory connectors of more expensive radios are not available in low tier radios.
Accordingly, there is a need for a method and apparatus for providing features normally available only on higher tier two-way radios on lower cost two-way radios that have limited accessory connection interfaces.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.